How Many Ways Are There to Define an Empty Slice in Go?

Defining an Empty Slice in Go

In Go, there are multiple ways to define an empty slice, including:

• var foo []int
• foo := []int{}
• foo := make([]int, 0)

Differences

• var foo []int initializes the slice to its zero value, which is nil. This means that foo will be a slice with zero length and capacity, and any attempt to access or modify its elements will result in an error.
• foo := []int{} and foo := make([]int, 0) both assign non-nil slices to foo. These slices have a zero length and capacity, but their underlying array pointer is set to an address reserved for 0-byte allocations.

Similarities

Regardless of which method is used, the following properties apply to all three statements:

• The slice length is zero: len(foo) == 0.
• The slice capacity is zero: cap(foo) == 0.
• The statement does not allocate memory.

Usage

Since len, cap, and append work with nil slices, var foo []int can be used interchangeably with foo := []int{} and foo := make([]int, 0) in most cases.

Short Variable Declarations

foo := []int{} and foo := make([]int, 0) can also be written as variable declarations with initializers:

• var foo = []int{}
• var foo = make([]int, 0)

Conclusion

All three methods of defining an empty slice are commonly used in Go code. The choice of which method to use depends on the specific requirements of your code.

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